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Full text of "The Cambridge Natural History"

M£GA THERIUM                                183

negatived this supposition. It has shown that the Armadillos
are in this matter the nearest relatives of Glossotherium, This
result is important as tending further to confirm the close inter-
relationship of all the American Edentates as contrasted with the
Old-World forms—a matter which has already been emphasised.
It is suggested, however, that the absence of under fur, which is
so well developed in the Sloth, and the difference shown in trans-
verse sections from the hair of Myrmecophaga, may he explained
by difference in habitat. Glossotherium lived under conditions
similar to those under which the Armadillos live to-day. Thus
the outer covering of the body became alike in the two cases, the
same needs supervening in both genera.
Lestodon is another allied genus, which seems to possess
canines. At any rate, in front of the four molars, and separated
from them by a diastema, is a smallish, somewhat canine-like
tooth, in both jaws.
Megalonyx and its allies are sometimes placed in a distinct
family, MegalonyoMdae. M~egalonyx itself had a skull very
like that of j&radypus, being shorter and not so elongated as
in the Mylodontidae. There is a strong tusk anteriorly, which4
is separated by a considerable space from the three molars lying
behind it. 33oth pairs of limbs seem to have possessed five toes.
This is a North American genus. It differs from the bulk of
the American Edentates in having a complete jugal arch.
Megatherium is the type of yet a third family, Megatheriidae,
of the Gravigrade Edentates. This creature is familiar from
the many restorations which have been built up, and from its
huge bulk, little short of that of an elephant. The skull, which
is small for the size of the creature, has a complete jugal
arch, from, the middle of which depends a downward process as
in other allied forms. The teeth grow to an extraordinary
depth, and there are five of them in the upper and four in the
lower jaw—on each side of course. The fore-limbs of the
Megatherium are very much more slender than the enormously
bulky hind-limbs, upon which and the equally massive tail the
animal seems to have supported itself while tearing down
branches of trees, upon whose leaves it fed. In the scapula
the acromion joins the coracoid as in Brady^ws; the clavicle is
large. The fore-limb is four-toed, and the hind-limb three-toed.
The latter has but one clawed digit (the third, i.e. the inner).